The present invention relates to a power assisted hydraulic control system especially suitable for clutches and brakes, particularly of motor vehicles, comprising a master cylinder, and master piston mounted to slide in the master cylinder and delimiting a control chamber, a hydraulic assistance unit comprising fluid-pressure means and a reservoir, and a distributor having a pressure port, a return port and an operating port which are connected respectively to the fluid-pressure means, the reservoir and a receiver by conduits, the distributor comprising a slide-valve having a plunger one end of which is exposed to the pressure of said control chamber and the other end of which is exposed to the pressure of the receiver, said slide-valve plunger being adapted to put said receiver under pressure in response to the pressure generated by the master piston in the control chamber.
In assisted hydraulic control systems of this kind, safety means are generally provided to permit manual operation in case of failure of the power assistance. These safety means generally entail a more complicated construction and are not always satisfactory.
The object of the present invention is to provide an assisted hydraulic control system of the above kind, which is especially suitable for clutches and brakes, which is free of the disadvantages described, and which, with a simple and convenient construction, has excellent normal and manual stand-by operation.